Japanese Patent No. 3902201, Japanese Unexamined Patent Publication No. 2004-184881 and U.S. Pat. No. 8,189,978 disclose an optical fiber in which a non-strippable resin layer is disposed on the outer circumference of glass and the non-strippable resin diameter is approximately 125 μm. The optical fiber is formed so that a general-purpose optical connector can be used.
In all of Japanese Patent No. 3902201, Japanese Unexamined Patent Publication No. 2004-184881 and U.S. Pat. No. 8,189,978, the non-strippable resin layer and a buffer layer on the outer circumference thereof are each formed by curing an ultraviolet curing resin. In this case, an acrylate group of the non-strippable resin and an acrylate group of the buffer layer form a covalent bond by a radical reaction to exhibit a strong adhesion force. Thus, removal of a coating layer on the outer circumference of the non-strippable resin layer is difficult. Furthermore, in the case of a ribbon structure in which a plurality of fibers are arranged laterally in a row, it is more difficult to remove the coating layer in simultaneous removal of a ribbon coating material and the buffer layer, and a problem is that a coating residue is generated on the outer circumference of the non-strippable resin layer.